sql 高级

        select top 50 percent * from persons (从"Persons" 表中选取 50% 的记录)

like操作符

eg:

        select * from Persons where city not like ‘%lon%‘

通配符

        select * from Persons where city like ‘%lond%‘

        select * from Persons where firstname like ‘_eorge‘

        select * from Persons where lastname like ‘c_r_er‘

        select * from persons where city like ‘[ALN]%‘  (从 "Persons" 表中选取居住的城市以 "A" 或 "L" 或 "N" 开头的人)

        select * from persons where city like ‘[!ALN]%‘  (从 "Persons" 表中选取居住的城市不以 "A" 或 "L" 或 "N" 开头的人)

IN操作符

        IN操作符允许我们在where子句中规定多个值

        eg:select * from persons where lastname in(‘adams‘,‘carter‘)

between 操作符

        操作符  between  ...and会选取介于两个值之间的数据范围，这些值可以是数值、文本、或者日期

        select * from persons where lastname between ‘adams‘ and ‘carter‘

        select * from persons where lastname not between ‘adams‘ and ‘carter‘

sql 高级

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